The present invention relates to a reimaging optical system adapted to re-form an image formed by an image guide on a solid-state imaging device, and an endoscope using the same.
In recent years, as endoscope systems are used in steadily expanding applications, there is rising expectation that they could be used in medical fields, e.g., for ordinary medical practices such as clearing up of phlegm from phlegm-stricken patients in wards, tracheal tube position checking in operating or treatment rooms for the purpose of maintenance of an airway before and after operations, and examination of non-resident patients.
Conventional heavy, bulky endoscope systems have difficulty carrying around and getting hold of positions after movement, and there is expectation that they could easily be carried around.
With a typical prior art portable endoscope having an end face of an image guide located on an imaging position, the formed image was guided through the image guide to a base end side of an insert so that an operator could examine sites under observation by way of an eyepiece optical system of an eyepiece portion. A problem with this was, however, that the operator was usually limited to a single person; the images could not been observed by two or more at the same time.
One possible approach to solving that problem is to use a digital camera's CCD and LCD so that an image by the image guide is formed on the CCD and viewed it through the LCD. With this approach, there can be an easy-to-carry endoscope set up that enables images to be observed by two or more.
Among reimaging optical systems so for known in the art, there is an optical system set forth in Patent Publication 1.
[Patent Publication 1]    JP(A)2003-84214
With the reimaging optical system of Patent Publication 1, however, an image by image fibers (on the end face of a bundle of image guide fibers) is hardly formed on a CCD that is generally used on a digital camera and has a diagonal length of 6.5 mm or longer. This is because the transverse magnification of a reimaging optical system adapted to form an image by the image fibers (the end face of the bundle of the image guide fibers) on the imaging area of the CCD is insufficient for this purpose. Even when the image by the image fibers is electrically enlarged, there are more noises and image quality deterioration that may otherwise interfere with observation.